I read once, in a book, about a lens that was an "inverse fisheye". Basically a hemispherical mirror mounted at one end of a glass tube.
I can't remember what it was called, nor can I find any record of its existance on the internet. Sadly, I no longer have the book to be able to reference it.
Has anyone heard of such a thing, and can name it, or better yet, got one, and some photos from it?